A thermomagnetic trip in an electrical switching device has the task of monitoring the current flowing through the switching device. If an overload is reached as a result of too great a current flowing through the device an opening of the contacts and thereby an interruption of the current flow is initiated by the thermal trip part of the thermomagnetic trip. The magnetic trip part of an electrical switching device is used for the detection of a short circuit. In the event of a short circuit an immediate tripping of the thermomagnetic trip is required, on the one hand to prevent danger to the downstream electrical devices or the users of these devices, on the other hand to protect the thermal trip part. The thermal trip part resides in such cases especially of a conductor through which current is flowing, able to be influenced by temperature, which has at least two terminals for connection to the circuit to be switched. The magnetic part of the trip mostly consists of a yoke in which a magnetic field is induced by the aforementioned current flow, and an armature able to be influenced by the current flow which, attracted by the large magnetic field induced during a short circuit, executes a movement in the direction of the yoke and causes the current to be interrupted itself or through downstream mechanisms.
A thermomagnetic trip of this type is known from DE 600 36 365 T2. An additional heating element, which is connected in series with the conductor able to be influenced by temperature, is provided in this thermomagnetic trip. It is located between the conductor able to be influenced by temperature and the terminal of the thermomagnetic trip able to be connected to a power lead. In this invention the additional heating element and the conductor able to be influenced by temperature are disposed within a yoke such that they have the same current flow direction. On the one hand this arrangement increases the temperature effect on the conductor able to be influenced by temperature and in addition the sensitivity of the magnetic trip is increased. However such an arrangement has been proved to have the disadvantage that, in order to achieve the same current direction in the additional heating element and the conductor able to be influenced by temperature, an increased space requirement in the transverse direction is needed to move the armature of the magnetic trip part. Furthermore in this thermomagnetic trip the conductor able to be influenced by temperature is connected via a wire directly to the customer terminal. Since the customer terminal has a significantly lower temperature than the conductor able to be influenced by temperature, heat is taken out of the conductor able to be influenced by temperature and thereby the response behavior of the conductor able to be influenced by temperature and thus of the thermal trip part is worsened.